diff --git a/src/libsystemd/sd-journal/journal-file.c b/src/libsystemd/sd-journal/journal-file.c
index 950b22f067..9216944e51 100644
--- a/src/libsystemd/sd-journal/journal-file.c
+++ b/src/libsystemd/sd-journal/journal-file.c
@@ -848,14 +848,16 @@ static int journal_file_allocate(JournalFile *f, uint64_t offset, uint64_t size)
         return journal_file_fstat(f);
 }
 
-static int journal_file_move_to(
+static int journal_file_move_to_full(
                 JournalFile *f,
                 ObjectType type,
                 bool keep_always,
                 uint64_t offset,
                 uint64_t size,
-                void **ret) {
+                void **ret,
+                uint64_t *ret_size) {
 
+        size_t window_size;
         int r;
 
         assert(f);
@@ -884,7 +886,27 @@ static int journal_file_move_to(
                         return -EADDRNOTAVAIL;
         }
 
-        return mmap_cache_fd_get(f->cache_fd, type_to_category(type), keep_always, offset, size, &f->last_stat, ret);
+        r = mmap_cache_fd_get(f->cache_fd, type_to_category(type), keep_always, offset, size, &f->last_stat, ret, &window_size);
+        if (r < 0)
+                return r;
+
+        /* The window is rounded up to whole pages, and may extend beyond the end of the file, which must not
+         * be accessed */
+        if (ret_size)
+                *ret_size = MIN((uint64_t) window_size, (uint64_t) f->last_stat.st_size - offset);
+
+        return 0;
+}
+
+static int journal_file_move_to(
+                JournalFile *f,
+                ObjectType type,
+                bool keep_always,
+                uint64_t offset,
+                uint64_t size,
+                void **ret) {
+
+        return journal_file_move_to_full(f, type, keep_always, offset, size, ret, /* ret_size= */ NULL);
 }
 
 static uint64_t minimum_header_size(JournalFile *f, Object *o) {
@@ -1106,8 +1128,9 @@ static int check_object(JournalFile *f, Object *o, uint64_t offset) {
 }
 
 int journal_file_move_to_object(JournalFile *f, ObjectType type, uint64_t offset, Object **ret) {
-        int r;
+        uint64_t size, available;
         Object *o;
+        int r;
 
         assert(f);
 
@@ -1129,7 +1152,7 @@ int journal_file_move_to_object(JournalFile *f, ObjectType type, uint64_t offset
                                        journal_object_type_to_string(type),
                                        offset);
 
-        r = journal_file_move_to(f, type, false, offset, offsetof(ObjectHeader, payload), (void**) &o);
+        r = journal_file_move_to_full(f, type, false, offset, offsetof(ObjectHeader, payload), (void**) &o, &available);
         if (r < 0)
                 return r;
 
@@ -1137,13 +1160,17 @@ int journal_file_move_to_object(JournalFile *f, ObjectType type, uint64_t offset
         if (r < 0)
                 return r;
 
-        r = journal_file_move_to(f, type, false, offset, le64toh(READ_NOW(o->object.size)), (void**) &o);
-        if (r < 0)
-                return r;
+        /* Usually the window of the header contains the whole object, which then needs no second lookup */
+        size = le64toh(READ_NOW(o->object.size));
+        if (size > available) {
+                r = journal_file_move_to(f, type, false, offset, size, (void**) &o);
+                if (r < 0)
+                        return r;
 
-        r = check_object_header(f, o, type, offset);
-        if (r < 0)
-                return r;
+                r = check_object_header(f, o, type, offset);
+                if (r < 0)
+                        return r;
+        }
 
         r = check_object(f, o, offset);
         if (r < 0)
@@ -4249,7 +4276,7 @@ int journal_file_open(
                 goto fail;
         }
 
-        r = mmap_cache_fd_get(f->cache_fd, MMAP_CACHE_CATEGORY_HEADER, true, 0, PAGE_ALIGN(sizeof(Header)), &f->last_stat, &h);
+        r = mmap_cache_fd_get(f->cache_fd, MMAP_CACHE_CATEGORY_HEADER, true, 0, PAGE_ALIGN(sizeof(Header)), &f->last_stat, &h, /* ret_size= */ NULL);
         if (r == -EINVAL) {
                 /* Some file systems (jffs2 or p9fs) don't support mmap() properly (or only read-only
                  * mmap()), and return EINVAL in that case. Let's propagate that as a more recognizable error
diff --git a/src/libsystemd/sd-journal/journal-verify.c b/src/libsystemd/sd-journal/journal-verify.c
index 79061940b3..d0a7c9eeaf 100644
--- a/src/libsystemd/sd-journal/journal-verify.c
+++ b/src/libsystemd/sd-journal/journal-verify.c
@@ -404,7 +404,7 @@ static int contains_uint64(MMapFileDescriptor *f, uint64_t n, uint64_t p) {
 
                 c = (a + b) / 2;
 
-                r = mmap_cache_fd_get(f, 0, false, c * sizeof(uint64_t), sizeof(uint64_t), NULL, (void **) &z);
+                r = mmap_cache_fd_get(f, 0, false, c * sizeof(uint64_t), sizeof(uint64_t), NULL, (void **) &z, /* ret_size= */ NULL);
                 if (r < 0)
                         return r;
 
diff --git a/src/libsystemd/sd-journal/mmap-cache.c b/src/libsystemd/sd-journal/mmap-cache.c
index f49ca12ba4..58d52ff41e 100644
--- a/src/libsystemd/sd-journal/mmap-cache.c
+++ b/src/libsystemd/sd-journal/mmap-cache.c
@@ -342,7 +342,8 @@ int mmap_cache_fd_get(
                 uint64_t offset,
                 size_t size,
                 struct stat *st,
-                void **ret) {
+                void **ret,
+                size_t *ret_size) {
 
         MMapCache *m = mmap_cache_fd_cache(f);
         Window *w;
@@ -386,6 +387,8 @@ found:
 
         category_attach_window(m, c, w);
         *ret = (uint8_t*) w->ptr + (offset - w->offset);
+        if (ret_size)
+                *ret_size = w->offset + w->size - offset;
         return 0;
 }
 
diff --git a/src/libsystemd/sd-journal/mmap-cache.h b/src/libsystemd/sd-journal/mmap-cache.h
index bf690536e9..24f492076e 100644
--- a/src/libsystemd/sd-journal/mmap-cache.h
+++ b/src/libsystemd/sd-journal/mmap-cache.h
@@ -39,7 +39,8 @@ int mmap_cache_fd_get(
         uint64_t offset,
         size_t size,
         struct stat *st,
-        void **ret);
+        void **ret,
+        size_t *ret_size);
 
 int mmap_cache_fd_pin(
         MMapFileDescriptor *f,
diff --git a/src/libsystemd/sd-journal/test-mmap-cache.c b/src/libsystemd/sd-journal/test-mmap-cache.c
index b59d5177f6..9fae3dcaa5 100644
--- a/src/libsystemd/sd-journal/test-mmap-cache.c
+++ b/src/libsystemd/sd-journal/test-mmap-cache.c
@@ -14,6 +14,7 @@ int main(int argc, char *argv[]) {
         char px[] = "/tmp/testmmapXXXXXXX", py[] = "/tmp/testmmapYXXXXXX", pz[] = "/tmp/testmmapZXXXXXX";
         MMapCache *m;
         void *p, *q;
+        size_t sp, sq;
 
         test_setup_logging(LOG_DEBUG);
 
@@ -30,21 +31,26 @@ int main(int argc, char *argv[]) {
         ASSERT_OK(z = mkostemp_safe(pz));
         (void) unlink(pz);
 
-        ASSERT_OK(mmap_cache_fd_get(fx, 0, false, 1, 2, NULL, &p));
+        ASSERT_OK(mmap_cache_fd_get(fx, 0, false, 1, 2, NULL, &p, &sp));
+        ASSERT_GE(sp, 2U);
 
-        ASSERT_OK(mmap_cache_fd_get(fx, 0, false, 2, 2, NULL, &q));
+        ASSERT_OK(mmap_cache_fd_get(fx, 0, false, 2, 2, NULL, &q, &sq));
 
         ASSERT_PTR_EQ((uint8_t*) p + 1, (uint8_t*) q);
+        ASSERT_EQ(sq, sp - 1);
 
-        ASSERT_OK(mmap_cache_fd_get(fx, 1, false, 3, 2, NULL, &q));
+        ASSERT_OK(mmap_cache_fd_get(fx, 1, false, 3, 2, NULL, &q, &sq));
 
         ASSERT_PTR_EQ((uint8_t*) p + 2, (uint8_t*) q);
+        ASSERT_EQ(sq, sp - 2);
 
-        ASSERT_OK(mmap_cache_fd_get(fx, 0, false, 16ULL*1024ULL*1024ULL, 2, NULL, &p));
+        ASSERT_OK(mmap_cache_fd_get(fx, 0, false, 16ULL*1024ULL*1024ULL, 2, NULL, &p, &sp));
+        ASSERT_GE(sp, 2U);
 
-        ASSERT_OK(mmap_cache_fd_get(fx, 1, false, 16ULL*1024ULL*1024ULL+1, 2, NULL, &q));
+        ASSERT_OK(mmap_cache_fd_get(fx, 1, false, 16ULL*1024ULL*1024ULL+1, 2, NULL, &q, &sq));
 
         ASSERT_PTR_EQ((uint8_t*) p + 1, (uint8_t*) q);
+        ASSERT_EQ(sq, sp - 1);
 
         mmap_cache_fd_free(fx);
         mmap_cache_unref(m);